Field of the Disclosure
Embodiments of the present invention relate to a touch sensing display device including a touch panel, and more particularly, to a touch panel capable of sensing both touch position and touch force, shortening a driving time for the touch sensing, and improving touch sensing efficiency, and an apparatus for driving thereof.
Discussion of the Related Art
In substitution for an input device such as a mouse or a keyboard according to the related art, a touch panel is widely used, wherein the touch panel facilitates direct input of information to a screen through the use of finger or pen. Thus, applications of the touch panel are gradually increasing due to an advantage of easy operation.
Recently, when a touch screen is applied to a liquid crystal display (LCD) device, a touch sensor is provided inside a liquid crystal panel so as to obtain slimness. Hereinafter, the touch panel will indicate the liquid crystal panel with the touch sensor provided therein.
According to a touch sensing method, the touch panel may be classified into a resistive type, a capacitance type, and an infrared sensing type. The capacitance touch panel has attracted great attention due to advantages of easy manufacturing and good sensitivity. The capacitance touch panel may be classified into a mutual capacitance type and a self capacitance type.
FIG. 1 is a cross sectional view illustrating a touch panel according to the related art.
Referring to FIG. 1, the touch panel 1 according to the related art may include a lower substrate with a plurality of pixels and a TFT array, an upper substrate with a color filter array, a polarizing film and a glass. On the lower substrate (TFT array substrate), there are a pixel electrode and a common electrode. In this case, the common electrode is used not only as a displaying electrode but also as a touching electrode.
FIG. 2 roughly illustrates touch electrodes of the touch panel according to the related art. The touch panel shown in FIG. 2 corresponds to the touch panel of all point self capacitance touch method for sensing all touch electrodes by the self capacitance method.
Referring to FIG. 2, the plurality of touch electrodes 10 are formed by grouping the common electrodes in a unit of plural pixels. In order to sense a touch in all the touch electrodes 10, each touch electrode 10 is connected with a touch driver 30 through a plurality of conductive lines 20.
In case of the touch panel 1 of all point self capacitance touch method, one frame period is divided into a display period and a touch sensing period, whereby display driving and touch sensing driving are carried out in a time division method.
For the display period, a pixel voltage is supplied to a pixel electrode, and a common voltage is supplied to a common electrode (touch electrode), to thereby display an image. For the touch sensing period, a touch drive signal is supplied to each touch electrode of the common electrode, and then a capacitance for each touch electrode is sensed for sensing whether or not there is a touch and sensing a touch position. For the touch sensing period, a signal is not applied to a thin film transistor (TFT) for each pixel, or a voltage whose level is the same as that of the touch drive signal is applied so as to reduce a parasitic capacitance.
In case of the touch panel 1 of all point self capacitance touch method, a size of touch driver is increased in accordance with the increased number of channels, and a touch efficiency is lowered due to the parasitic capacitance. Also, a touch driving time is increased due to the large number of channels so that it is difficult to secure the touch driving time. Meanwhile, the display period is shortened to sufficiently secure the touch driving time.
Recently, there is an increasing demand for a touch panel which facilitates sensing a touch force as well as the touch position. However, in case of the related art touch panel 1, the common electrode is used as the touch electrode so that it is difficult to sense the touch force due to a structural problem of the touch electrode.
In order to sense the touch force, it is necessary to provide an elastic dielectric on the TFT array substrate. However, the elastic dielectric might cause a problem in the display driving. Thus, there is a limitation on application of the elastic dielectric to the TFT array substrate. Also, a manufacturing process for the elastic dielectric is complicated and a manufacturing cost is also increased. Furthermore, the capacitance is slightly changed by the touch force applied to the elastic dielectric so that it is difficult to realize a required level in the touch force sensing efficiency.